Stimuli‐Responsive Molecular Photon Upconversion

Abstract

The addition of stimuli‐responsiveness to anti‐Stokes emission provides a unique platform for biosensing and chemosensing. Particularly, stimuli‐responsive photon upconversion based on triplet–triplet annihilation (TTA‐UC) is promising due to its occurrence at low excitation intensity with high efficiency. This Minireview summarizes the recent developments of TTA‐UC switching by external stimuli such as temperature, oxygen, chemicals, light, electric field, and mechanical force. For the systematic understanding of the underlying general mechanisms, the switching mechanisms are categorized into four types: 1) aggregation‐induced UC; 2) assembly‐induced air‐stable UC; 3) diffusion‐controlled UC; and 4) energy‐transfer‐controlled UC. The development of stimuli‐responsive smart TTA‐UC systems would enable sensing with unprecedented sensitivity and selectivity, and expand the scope of TTA‐UC photochemistry by combination with supramolecular chemistry, materials chemistry, mechanochemistry, and biochemistry.

Full-type photoluminescence from a single organic molecule for multi-signal temperature sensing

“…DF of the chromophore originates from triplet-triplet annihilation, which has been well reported in the literature. [59][60][61] Thermoresponse of multiple luminescence PL of the chromophore is highly sensitive to temperature. With lowering temperature, both fluorescence and phosphorescence emissions are enhanced.…”

Dynamic upconversion multicolour editing enabled by molecule-assisted opto-electrochemical modulation

“…The ability to dynamically control optical functionalities of the upconversion medium by modulating external stimuli, such as temperature, pressure, magnetic or electric field, will facilitate development of multifunctional, nonlinear optoelectronic devices 7 – 9 . In particular, there is strong demand for electrical control over optical properties of upconversion nanomaterials, as such control will not only allow monolithic integration of photonic elements with optoelectronic functionalities but will also lead to many intriguing phenomena in nonlinear regimes 10 – 12 .…”

Unusual light-driven amplification through unexpected regioselective photogeneration of five-membered azaheterocyclic AIEgen

“…9,10 In addition, compounds containing fivemembered azaheterocycles have found potential applications in various areas including catalysis, agriculture, electronics, etc. [11][12][13][14][15][16][17][18] Considering their great value in industrial application and academic research, it is far from enough to obtain them by simple separation from natural products. Therefore, great endeavor has been put on exploring artificial synthetic methods for five-membered heterocycles, particularly the fused ones.…”